Purpose of the Manual
The purpose of the LCM is to provide information useful for advance planning of lane closures that will minimize traffic impacts and motorist delays while promoting safety for work crews and the traveling public. The LCM covers MnDOT owned and operated roadways within the Metro District.
Traffic congestion and backups may contribute to the cause of crashes and motorist delays. Traffic management practices that attempt to reduce congestion have a documented positive effect on crash rates, motorist travel times, and travel time reliability. Planned lane closures that do not cause a traffic flow "bottleneck" will cause only minor to moderate levels of congestion and backup and are an effective traffic management strategy.
How Allowable Lane Closures are Determined
Traffic flow volumes from RTMC detectors and tube counters is collected, analyzed and formatted to display "Allowable Lane Closure" figures based on roadway location and time of day.
Determination of allowable lane closures is based on the Highway Capacity Manual and practical experience. On the freeway system, the manual assumes that one travel lane typically carries 1800 vehicles per hour. If the traffic volume demand is 1800 vehicles per hour or less, then only one travel lane must be open. If the traffic volume demand is between 1800 and 3600 vehicles per hour, then two travel lanes must be open. This pattern using increments of 1800 vehicles per hour continues as traffic volume demand increases. These "open lane" requirements are based on documented findings and observations that traffic flows less efficiently past work zones than it does through non-work zones.
Compiling and interpreting data for this application is subject to certain constraints and considerations. Seasonal and even daily traffic volume fluctuations are normal and will be observed frequently. The actual median traffic volume value seldom occurs, but a volume that is close to the median will often occur. The "Allowable Lane Closure" figures given in this manual have been smoothed to remove some of these data fluctuations and to make this manual easier to apply in the field. Special events and detours on other nearby parallel and intersecting roads may also change traffic volume patterns on a highway - see "Impact Sensitive Routes Review". These special circumstances must be observed and managed in the field as they occur.
The manual is divided into sections by roadway and each roadway is divided into segments. Segments are generally determined by the number of continuous lanes available along a highway corridor. The index maps illustrate where each roadway is broken down into numbered segments. The numbered segment directs the user to the correct page of the manual that provides tabulated traffic data. A system of shading is used to display the number of lanes that can be closed for each hour of the day. Users should note that lane closures on signalized roads have special Allowable Lane Closure figures that depend on the proximity of the closure to the signals. A lane closure that is closer than 500 feet to the signal may reduce the number of lanes that can be closed.